Generally, a portable electronic device such as a cellular phone, a notebook computer, a camcorder, a Personal Digital Assistant (PDA), and the like has a secondary cell such as a rechargeable battery (for example, Nickel-Cadmium battery), a lead storage battery, a Nickel Metal Hydride Battery (NiMH), a Lithium Ion Battery, a Lithium Polymer Battery, a metal lithium battery, an air zinc storage battery, and a user may charge and use a battery by connecting the portable electronic device mounting the battery thereon to a charger. The charger may exist inside the portable electronic device or exist as a separate external device. The charger may be connected to an external power terminal to supply power applied from the external power terminal to the battery, thereby charging the battery. Also, the charger may control power applied from the external power terminal to be supplied constantly to the battery. Here, the external power source may be DC power output from an adapter (for example, Travel Adapter (TA)).
For example, the adapter converts AC power of 220V to a voltage of 5V to provide the same to a charger or a charging IC inside an electronic device, and the charger or the charging IC inside the electronic device converts a DC voltage of 5V provided from the adapter to a DC voltage of 2.8 V˜4.35 V to control a charging current. Also, the charger or the charging IC may provide a controlled charging current to an internal battery inside the electronic device to charge the battery.
A charging current of the battery is set in advance and fixed by a manufacturer of an electronic device. The manufacturer may set a charging current in advance with consideration of an expected charging time, heat emission, and the like. Recently, as an electronic device such as a smartphone has a high performance in order to provide various functions (for example, an Internet search service, a DMB service, a location-based service, and a multimedia service), heat emission problem emerges. To solve this problem, the manufacturer sets a charging current passively. In other words, the manufacturer sets a charging current in advance such that surface heat emission of the electronic device does not exceed 45 degree with consideration when charging a battery under a state (referred to as a ‘heavy use’) where applications that cause much heat are executed inside the electronic device by a user.
However, since charging is performed using the same charging current set in advance even when a user does not use relevant applications, it is inefficient. In other words, since a charging current is set in advance with reference to an environment where predetermined heat emission occurs due to execution of an application, a battery may be charged using the charging current set in advance even under an environment where applications are not executed by a user.